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May 11, 2011 -- Infants who are exposed to marital discord are more likely to have trouble sleeping during infancy and when they approach the toddler stage, a study shows.

Researchers evaluated more than 350 families when their babies were 9 months old and 18 months old. All the babies had been adopted because the scientists wanted to eliminate the chance that any behaviors between parents and kids weren’t caused by shared genes or personality characteristics.

The main finding: Instability in the parents’ relationship when the children were 9 months old predicted the babies would have trouble falling asleep and staying asleep when they were 18 months old.

The study is published in Child Development.

Impact of Marital Discord

Researchers set out to discover whether marital instability -- for example, parents contemplating divorce -- might be related to the children’s sleep problems later in their lives.

They wanted to check out the possibility that changes in brain systems involved in development of sleep patterns might reflect the impact of stress in the family on very young kids.

“Our findings suggest that the effects of marital instability on children’s sleep problems emerge earlier in development than has been demonstrated previously,” says study researcher Anne M. Mannering, PhD, in a news release. Mannering is an instructor of human development at Oregon State University.

“Parents should be aware that marital stress may affect the well-being of their children even in the first year or two of life,” Mannering says. She also says that if these problems persist, they can “correlate with problems in school, inattention and behavioral issues.”

The researchers also found that sleep problems of children did not predict marital instability.

The research was funded by the National Institutes of Health. Mannering was employed at the Oregon Social Learning Center when she and her colleagues worked on the study.

Measuring Marital Instability

Mannering says the study is the first done on the link between marital issues and infant sleep that unambiguously eliminates the role that shared genes could play in sleep and other behaviors.

Marital instability was ranked using a standard four-point research measure, with couples answering questions independent of one another, such as, “Has the thought of separating or getting a divorce crossed your mind?”

The couples were mostly middle class, white, and fairly educated; all had adopted a baby within the child’s first three months of life.

The researchers say they are now investigating whether the relationship between marital instability and children’s sleep problems continues after age 2, and also the role that the parent-child relationship might play in such associations.